Carbondale, Colorado’s energy conservation code requirements

Carbondale is currently (June 2019) on the 2009 IRC (International Residential Code), the 2012 IgCC (International Green Construction Code) and the 2015 IECC (International Energy Conservation Code).


Carbondale has adopted the 2015 IECC and has a REBP (Residential Efficient Building Program). The chart below is the crux of understanding the energy code compliance.

Link to adoption…

Carbondale REBP

Link to REBP guidelines and REBP checklist here…

The required points refer to the REBP checklist. Points are earned by including features in the house like; efficient framing, water conservation, chemical reduction, etc. Refer to the guidelines to understand how to fill out the checklist. Extra points are awarded for above code HERS (Home Energy Rating Score), infiltration rates and solar.

Currently (June 2019) the Town enforces the HERS maximum on the chart in lieu of the ERI (Energy Rating Index) path compliance limits as listed in the 2015 IECC. Which is quite a bit easier to obtain than the 2015 ERI limit for zone 6; which is 54 for any sized dwelling. But ERI 54 will never become the limit, because the Town adopted the ERI number from the 2018 IECC, ERI 61. Currently, the Town is not considering ADUs (Accessory Dwelling Units) as their own unit, that needs its own; REBP submittal, HERS rating and blower door infiltration test.

HERS ratings are not mandatory, but it would be unlikely to show 20% better than code with only a Total UA calculation (REScheck). Getting to a HERS of 60 or 70 is pretty easy, even without renewables. If a project is small enough to get through under the Prescriptive path or Total UA Alternative, the project will still need an infiltration test report showing 3 ACH50 (Air Changes per Hour at 50 Pascal) or better. And duct leakage testing if any ductwork leaves the thermal envelope.

Other random amendments;

  1. Carbondale has amended their Climate Zone to 6.
  2. Maximum infiltration rate changed to 5.0 ACH50.
  3. Alternate maximum infiltration rate adopted: .24 CFM50 per square feet of thermal envelope area.
  4. 1.2 CFM/watt minimum efficacy for HRV/ERVs (Heat Recovery Ventilators or Energy Recovery Ventilators) fan motors.
  5. ERI compliance level is modified to 61.

Confluence can perform these tests and produce these compliance reports. Please call us early in the process so we can help you optimize the insulation and comply with the energy code in the most cost-effective way.


Carbondale is on the 2009 IBC (International Building Code), but they have also adopted the 2012 IgCC (International Energy Conservation Code).

Link to Carbondale’s heavily amended adoption of the IgCC here…

Navigating the IgCC is a deep subject, but expect it touch every phase of your project. The code requires above IECC insulation and infiltration mitigation, construction waste tracking and structured plumbing. The code requires third-party inspections and testing for the envelope. Confluence has been the code compliance and envelope consultant for six IgCC projects now. The Town of Snowmass Village has also adopted this code. Please calls us early in the process if you are planning a commercial project in The Town of Carbondale or The Town of Snowmass Village.

Jump to ICC’s overview of the International Green Construction Code…


Jump to Pitkin County’s energy conservation code compliance page…

Jump to Aspen’s energy conservation code compliance page…